This may be naive, but where is the Ubuntu install file to be flashed onto an Android device? I see no links to that image in the instructions or release notes. Thanks!
Have you installed the phablet-tools on your desktop? From the install instructions,
Once you've got that running, then putting your unlocked phone/tablet into fastboot and running
will select the right image for you and download and install it. The full instructions are at https://wiki.ubuntu.com/Touch/Install
If you want to get at it later on for whatever reason, the image files will have been placed in your user Downloads/phablet-flash folder